1. Field of the Invention
This invention relates to an exposure control circuit for a camera, and more particularly to an exposure control circuit for a photographic camera in which a shutter release locking means is provided for locking the release of the shutter in the camera when the ambient temperature of the camera becomes beyond the range wherein temperature compensation is possible.
2. Description of the Prior Art
It has been known in the art to lock the shutter in a photographic camera when the voltage of the power source in the exposure control circuit of the camera falls below a predetermined lower limit or when the scene brightness is below a predetermined lower limit. In order to lock the shutter, a locking means is provided in the camera in connection with the exposure control circuit including a power source and a photodetector.
The exposure control circuit becomes inoperable not only in the case that the voltage of the power source falls below a predetermined level, but also in the case that the power source and other electric circuit elements are subjected to an abnormal temperature.
If the automatic exposure control circuit is operated when the ambient temperature is beyond the range in which the circuit is temperature compensated, the exposure is not correctly controlled and accordingly a color failure or a density failure occurs in the color film exposed in the camera. Therefore, it is desired that the shutter be automatically locked when the ambient temperature is beyond the range in which the circuit is capable of being temperature compensated.